The invention relates to motorcycles, and more particularly to motorcycles having liquid-cooled engines.
Motorcycles having liquid-cooled engines are known. Typically, the liquid coolant flows in a circuit having a radiator, a pump, and a water jacket surrounding each of the engine cylinders. Liquid coolant is pumped from the outlet of the radiator to the inlet of the water jacket via a feed line. Heat generated in the cylinders is transferred to the liquid coolant in the water jacket. A return line extends between the outlet of the water jacket and the inlet of the radiator to transfer the heated liquid coolant back to the radiator, thereby removing heat from the cylinders. The heated liquid coolant circulates through the radiator and is cooled by air flowing around the radiator as the motorcycle moves.
The flow of liquid coolant in the above-described coolant circuit is controlled, in part, by a thermostat assembly that provides variable flow restriction of the coolant through the return line. The thermostat assembly includes an inlet, an outlet, and a temperature-sensitive valve positioned between the inlet and the outlet. The valve is configured to selectively allow or prevent coolant from flowing through the outlet and into the return line. When the temperature reaches a predetermined level, the valve opens, allowing heated coolant to return to the radiator.
U.S. Pat. No. 4,519,473 discloses a motorcycle having a single-cylinder liquid-cooled engine. The water jacket extends around the cylinder and forms a portion of the cylinder head. The thermostat assembly is mounted on the cylinder head adjacent the exhaust port of the water jacket.
With larger, two-cylinder liquid-cooled motorcycle engines, the design and placement of the thermostat assembly is more complicated. Two-cylinder engines have two separate water jackets, one water jacket surrounding each cylinder. The thermostat assembly must be adapted to receive coolant from both water jackets. Typically, rubber hoses are used to provide fluid communication between each of the water jackets and the thermostat assembly. Metal hose clamps are required to seal the various connections between the hoses, the water jackets, and the thermostat assembly.
The use of rubber hoses typically necessitates the remote placement of the thermostat assembly from the cylinders. Often, the two individual hoses extending from the two water jackets must first come together at a junction so that the coolant can enter the thermostat assembly via a single inlet. Significant space is needed in which to bring the two hoses together, form the necessary junction, and combine the separate coolant flows into a single stream flowing through a single hose. Because of the space requirements, the thermostat assembly is typically remote from the outlets of the water jacket, resulting in a less than compact motorcycle engine cooling system.
The present invention provides an improved thermostat housing assembly for a two-cylinder, liquid-cooled motorcycle engine. The thermostat housing assembly has a compact design that enables the thermostat housing assembly to be directly connected to the two water jacket outlets, thereby resulting in a compact engine cooling system. No rubber hoses or hose clamps are required to provide fluid communication between the water jacket outlets and the inlets of the thermostat housing assembly. Rather, the thermostat housing assembly includes two short connector tubes, one connector tube extending from each of the two thermostat housing inlets. The connector tubes are plugged directly into the respective water jacket outlets to create the necessary fluid communication lines.
The thermostat housing assembly also communicates with a passageway in the crankcase that provides a circulation path for the coolant flowing through the water jackets. When the valve is closed, coolant is pumped into and flows through the water jacket, exits the water jacket into the thermostat housing assembly, and flows back to the water jacket circuit through the passageway in the crankcase. The thermostat housing assembly is mounted directly on the crankcase, adjacent the passageway, thus further avoiding the need for rubber hoses and hose clamps.
The thermostat housing assembly can also include a temperature sensor positioned adjacent the inlet side of the valve to measure the temperature of the coolant flowing through the water jacket. The measured temperature of the coolant is relayed to the engine control unit.
With the improved thermostat housing, the installation of the coolant system is greatly facilitated. Additionally, a more compact motorcycle design is achieved.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.